Traditionally, human leukemias have been diagnosed and classified by morphologic and histochemical techniques. Recently, specific enzyme analyses and cell surface antigens have refined the classification of acute lymphocytic leukemia. With the exception of morphologic subvariants such as monoblastic and promyelocytic leukemia, there has been little success in subclassifying the acute myeloid leukemias. We propose the application of recombinant DNA technology to construct a "library" of gene sequences corresponding to different developmental stages of acute myeloid leukemia. The library will be constructed from freshly isolated leukemic cells and from two "immortal" leukemic cell lines. The library will be used to classify human leukemias according to their expression of particular gene sequences. We will then make the appropriate correlation between such a classification and traditional morphology, histochemistry, response to treatment and the natural history of leukemia in a given patient. If any unique leukemia-related sequences are detected, these may serve as diagnostic probes for response to therapy and to relapsed disease.